This invention relates to a paint system including a flexible conduit or hose arrangement to supply a liquid coating composition from a paint supply system to a spray gun. More particularly, this invention relates to an improved spray gun for the paint system.
As those familiar with the prior art will appreciate, in previous paint supply systems, a base coat of paint is applied at a first station and then the article, such as an automobile body, is conveyed to a new station where a clear coat paint is applied, the clear coat paint adding the feeling of depth to the paint. The ability to apply a clear coat and a base coat at the same time would provide a dramatic reduction in the cost of painting the car in the sense that half of the spray booths could be eliminated or deactivated and therefore half of the equipment and half of the manpower could be eliminated from the painting operation.
Additionally, the modern factory is typically spread out and paint booths are not localized in one area or arranged so as to be parallel to one another. As a result, the use of a series connection between paint booths requires extensive tubing, particularly when the paint must be supplied to opposite sides of each booth. Accordingly, it would be desirable to minimize the number of lines needed to supply paint in a paint system and the cost associated with these lines.
A continuing problem associated with the spray application of liquid paints is the presence of foreign particulate matter in the liquid paint supply which causes imperfections on the surfaces of the article being spray painted, frequently necessitating a refinishing or repainting thereof. Such foreign particulate matter, sometimes referred to as xe2x80x9cseeds,xe2x80x9d or xe2x80x9cstrings,xe2x80x9d or xe2x80x9csnottersxe2x80x9d are formed in many instances as a result of an agglomeration of the paint constituents during standing or recirculation of the liquid paint necessitating removal prior to discharge through the spray nozzle. The foregoing problem is particularly pronounced in recirculating type liquid paint systems, although they are present in direct line systems as well.
Recirculating paint supply systems conventionally comprise a mixing tank equipped with suitable agitation for maintaining the liquid coating composition uniformly mixed and a pump for transferring the liquid coating composition under a desired pressure to a manually manipulable supply conduit connected to the spray nozzle. A suitable return hose is provided for returning the excess quantity of paint back to the mixing tank for recirculation and to keep the paint in suspension. Typical of such a system is the recirculating paint supply system shown in U.S. Pat. No. 5,060,861, the specification of which is incorporated herein by reference. In this paint supply system, the supply and return hoses are interconnected by suitable fluid fittings so as to form a single conduit having coaxial passages for supplying and returning the liquid composition.
This and like paint systems typically will utilize many different fittings, connectors and coupling arrangements to complete the necessary fluid interconnections. Such fittings are often generally made of metal which can result in the conduit being relatively heavy. However, the paint supply hoses or unitized fluid conduit, and the associated fluid fittings, should be as light as possible to reduce operator fatigue and enable the operator to manipulate the position of the spray gun.
Moreover, conventional spray guns are also generally made of metal which results in the spray gun, including the fittings to be relatively heavy. This weight may cause operator fatigue or ailments based upon the continuous and repetitive use of the heavy spray gun, which typically weighs about 22 ounces. Still further, as the work day draws on, this fatigue increases which may cause an appreciable decrease in finish quality of the object being coated. This decreased quality generally occurs because the operator may angle the spray delivered from the spray gun as opposed to maintaining the spray substantially perpendicular to the object which is desired.
Seals and filters are also included in the paint supply line to seal the interconnections as well as to remove particulate matter from the paint being provided to the spray gun. In spite of the seals and filters, foreign matter can still be present. For example, the quick connectors used for the spray gun tend to create spit at the quick disconnect upon disconnecting which is generally not noticeable but, when dry, will cause leakage and contamination to occur. Further, to prevent leakage, it is known to cover the threaded sections of fluid fittings with pipe dope and then assemble the fittings. While this arrangement works well in many fluid sealing applications, it has several disadvantages. First, a pipe fitter must be called to assemble or disassemble the unit, which can be an inconvenience. Further, exposed threads create voids in the joint between the components which causes paint to accumulate and generates paint particles (dirt, etc.) that will be sent downstream and end up on the car, resulting in the need to rebuff and/or repaint the car.
Various flow control devices or paint restrictors are also used with paint supply systems. In many cases such prior art constructions have been handicapped by their tendency to become plugged over periods of use, necessitating frequent replacement and/or downtime to permit cleaning to restore them to proper operating conditions. The build up of deposits in such flow regulators cause a progressive decrease in the pressure of the liquid coating composition supplied to the spray nozzle, thereby resulting in variations in the quality and thickness of the coating, thus detracting from their use.
Moreover, a flow control device must include an element that moves relative to its valve body in order to change the flow rate. For example, a conventional ball valve has a rotatable ball member through which fluid can flow and seal portions positioned at the opposing upstream and downstream faces of the ball to inhibit flow therearound. Extended use of the valve member in one flow position can result in paint coagulating in voids formed around the seal portions. When the ball member is rotated, paint portions can break loose, thus detracting its use. Paint flakes, particles and dirt can result from the mating of fluid connector members, notwithstanding a seal being positioned to prevent flow around mated portions.
Accordingly, it would be desirable to limit or replace the use of threaded fittings with compression fittings, or those that use only pressure, thereby eliminating voids which tend to cause the paint to accumulate.
Moreover, it would also be desirable to reduce the weight of the conventional spray gun and fittings, thereby reducing operator fatigue and increasing finish quality.
The benefits and advantages of the present invention are obtained in a recirculating paint supply system that has a substantially flexible recirculating fluid conduit connected at one end to a spray gun and at its other end to supply and return lines of a paint supply.
To selectively connect and disconnect the supply and return lines of the paint system to the supply and return hoses of the recirculating conduit, a series of ball valves are interconnected to form an H-shaped fluid connector assembly. According to an exemplary embodiment of this invention, a funnel shaped seal is sandwiched between mating frustoconical surfaces of the interconnected ends of the valves whereby to form a compression seal. Alternatively, the interconnected ends of the valves may be coupled by the use of flare fittings using mating conical surfaces. Additionally, the interior surfaces of the valves which contact the paint composition are comprised of stainless steel or other suitable metal, that is resistant to attack by the paint.
According to a preferred embodiment of the paint system of the present invention, the H-shaped fluid connector assembly includes a connecting mechanism having an annular member pivotably mounted to each handle of the ball valves. When the annular member is moved with a clockwise force, each handle on each ball valve is simultaneously moved to simultaneously open and close the ball valves. This allows the recirculating conduit to be quickly checked for pressure differential or loss.
According to a preferred embodiment of the paint system of the present invention, the discharge end of the recirculating fluid conduit has a fluid fitting secured thereto. In an exemplary embodiment, helical convolutions having a predetermined pitch width extend radially outward from the fitting, and a guard for protecting the outer periphery of the conduit and providing strain relief to conduit is secured to the helical convolutions. The fluid fitting includes a rotatable coupling nut, and the guard includes a wire helically coiled to form a generally cylindrical member that encircles an axial portion of the conduit and extends axially away from the fitting. A portion of the wire helix has the same predetermined pitch width as and threadably engages the convolutions, coupling rotation of the nut tending to tighten the engagement of the coil with the convolutions.
According to another preferred embodiment of the paint system of the present invention, particularly applicable for the manual spray application of liquid coating compositions, a quick disconnect connector assembly is provided to enable the rapid connection and disconnection of the fluid conduit and prevent unwanted spit of paint during the connection or disconnection to the spray gun. The quick disconnect connector assembly comprises a valve body having a bore, a tubular fluid conduit having a stem which is inserted into the bore, a seal element having a passage positioned in the bore, and a first closure member normally engaged with the seal for sealing the passage and movable from sealed engagement by the inward insertion of the stem. The stem and the seal passage are dimensioned such that the forward end portion of the stem is adapted to establish sealing engagement with the wall of the seal passage both when the stem has been partially inserted into the passage but prior to engaging the first closure member, during which time no flow is permitted through the connector assembly, and also when fully inserted into the passage, whereby to move the first closure member from its flow preventing engagement with the seal.
According to another preferred embodiment of the quick disconnect fluid connector assembly of the present invention, the stem includes a second closure member to seal the stem when it is removed from the bore of the valve body. When the stem is inserted into the bore and the first closure member is moved from engagement with the seal, the pressure and fluid in the fluid conduit causes the second closure member to be moved to enable the flow of fluid through the stem. When the stem is removed from the bore and the first closure member engages the seal, the pressure and fluid downstream of the stem causes the second closure member to be moved to inhibit flow of fluid through the stem, thereby inhibiting the stem from spitting fluid during disconnection.
According to another preferred embodiment, a flow control device of the present invention comprises a valve body having opposite end portions and a bore extending between the end portions, a closure member, including a rotatable ball member in the bore and having a passageway therethrough, for selectively opening and closing the bore to permit and prevent flow through the bore, and seal means, operating to encapsulate the ball member, for sealing the bore to prevent unwanted fluid leakage. The seal operates to eliminate voids in which paint could collect and break free to contaminate the paint system during rotation of the ball.
Further, certain of the connection elements provided in the flexible recirculating conduit are comprised of a suitably configured polymeric material which combines strength and functional relationships and decreases weight, the material preferably being of a glass-filled nylon with a ceramic. Importantly, the fluid connection elements connecting the supply to the inlet end of the conduit are comprised of stainless steel.
Still further, the improved spray gun of the present invention is also comprised of a suitably configured polymeric material, such as glass-filled nylon with a ceramic. This material reduces the overall weight of the spray gun while at the same time increasing the overall strength and durability of the spray gun. Moreover, the improved spray gun further includes enlarged air passages which allows a greater volume of air to pass through the spray gun to achieve better atomization at any pressure. Such an improved spray gun, decreases operator fatigue, increases durability, and further increases overall surface quality of the paint finish because of the reduced fatigue and the better atomization.
The present invention overcomes many of the problems and disadvantages associated with prior art constructions, providing simple, economical yet durable devices which can be directly connected to the fluid inlet of a conventional spray gun or the improved spray gun and is easily manipulable by an operator. Significantly, flakes and other particles which could interfere with the quality of the painted surface are inhibited and possibly eliminated.
Additional benefits and advantages of the present invention will become apparent upon a reading of the description of the preferred embodiments taken in conjunction with the accompanying drawings.